The present invention relates to a planetary roller system, in particular for a device for extending bones, with two elements that can be moved in relation to one another and that are interconnected via at least one drive element.
Devices of this kind are known and commonly available on the market in a wide variety of formats and designs. They are used in particular also as a drive means for devices for extending bones. They can be inserted into a bone cavity or a medullary space of a bone, and distraction can take place after the bone has been cut through.
A disadvantage is that conventional planetary roller systems for distraction devices cannot take up or generate very high forces and cannot be exactly and precisely manufactured in miniature format. In addition, they must be able to be easily taken apart for cleaning, and, particularly when used in medical instruments, they must be able to be fitted very quickly and simply.
Specifically in the design of distraction devices having a very small cross section, planetary roller systems are used as drive systems whose cross sections have to have a very small diameter. In order to very high forces during distraction or movement of one element in relation to the other element, conventional planetary roller systems are not suitable as drive elements or drive units.
JP 2001 330087 A discloses a differential gear for a vehicle, in which three planetary rollers are mounted securely in a planetary roller cage.
A similar mounting of planetary rollers in planet carriers or cages is disclosed in DE 44 21 428 C1 and WO 01/81787 A.
The object of the present invention is to make available a planetary roller system, in particular for a device for extending bones, which overcomes the stated disadvantages and with which straightforward assembly and disassembly is possible in a simple, inexpensive and precise manner, and with which very high forces can be transmitted, the aim being for the planetary roller system to have very small diameters.